This Presentation is prepared to demonstrate the Internal Microprocessor Architecture 8086.

2. Group Members
 12063122-011 ( M.Noman
)
 12063122-017 ( Hafiz
Hamid )
 12063122-029 ( Salah
Uddin Ayubi )
 12063122-037 ( Mubashar
Naeem )
 12063122-023 ( Safi ur
rehman Tabasum )
 University Of Gujrat
(Pakistan)

3. Internal microprocessor
architecture
 ON the basis of programing

4. Microprocessor’s type
Internal structure of microprocessor should be known
Single core 1. single task at any time
2.access whole memory at
the same time by any program
Dual core 1.multiple task at any time
2.access specific memory by
any task

5. Programing model
Program visible : 8086,8088
Registers are used directly
during programing
Program invisible : 80286 and above
1. Registers are not accessible
directly during programing
2. Can be used indirectly

6. Programing model
Program visible : 8086,8088
Registers are used directly
during programing
Program invisible : 80286 and above
1. Registers are not accessible
directly during programing
2. Can be used indirectly

8. Only for 64 bit

9. cont.….
 We can’t access these register with the instruction used
to access general purpose register AX,BX etc….
 To access the low order byte of R8 use R8B
 To access the low order word of R10 use R10W

10. Cont.……

11. Condition flag

12. Special purpose flag
 The 6 Segment Registers are:
 Stack Segment (SS). Pointer to
the stack.
 Code Segment (CS). Pointer to
the code.
 Data Segment (DS). Pointer to
the data.
 Extra Segment (ES). Pointer to
extra data ('E' stands for 'Extra').
 F Segment (FS). Pointer to more
extra data ('F' comes after 'E').
 G Segment (GS). Pointer to still
more extra data ('G' comes after
'F').

13. Details about registers

14. Remember
 R_ _ used in 64 bit MP
 E_ _ used in 32 bit MP
 (E stand for extended)
 Register can access as R_ _ , E_ _ , _ _ , _L ,_ H

15. Multipurpose or general purpose
register

16. Accumulator (RAX)
 Used for IO operation, rotate, shift, multiplication
and division

17. Base index (RBX)
 Hold the offset address of a location In a memory
system
 Also address the memory data

18. Count Register (CX)
 Used as default counter for various instruction like
repeated string, shift, rotate(CL), loop etc…
 Hold the offset address of memory data
 Address memory data

19. Data Register (DX)
 Hold the part of the result from a multiplication or
part of the dividend before division.
 Address memory data

20. Stack Pointer : pointing the top of the stack
in stack segment
Base Pointer: contain the offset address within
data segment
Source index : Used as a pointer to a source in
stream operations
Destination index : used as a pointer to
destination in stream
operations
 All these register also used for based
indexed, register indirect addressing

21. R8-R15
These register are only found in Pentium 4 and core2 if
64-bit extensions are enables
Used as general purpose register
In most application these registers remain unused

22. Special Purpose Register
Instruction pointer (IP) :
point to the next
instruction in a program located within
the code segment
Stack Pointer :
pointing the top of the stack
in stack segment to store data

23. Flag Register
Determine the current state of the process
Modified automatically after M.Operations
Conditional Flag
Carry flag:
indication of overflow condition for
unsigned integer and hold carry
Auxiliary flag :
indication the carry/borrow from
lower nibble to high nibble(D3-D4)

24. Parity flag : indication of parity of the result
Zero : set if result is zero
Sign flag: In signed magnitude format, if the
result of the operation is negative,
sign flag is set

25. Control Flag
Control the operation of the execution unit
 Trap flag : if set, then debugging operation
is allow
 Interrupt flag: control the operation of interrupt
request.
note : set by instruction STI
clear by instruction CLI
 Direction flag : used in string operation. if it is set,
string byte is accessed from higher memory
address to lower memory address

26. Flags for 32,64-bit
 IOPL (IO privilege level) :
used to select the privilege level for IO
devices.
 if the current privilege level is 00 ,IO
execute without hindrance
 if 11 then an interrupt occur and
suspended the execution

27.  NT (nested task) :
 indicate whether the task is nested with
other or not
RF (resume) :
 resume flag is used with debugging to
control the resumption of execution after
the next instruction

28. VM (virtual mode) :
 This allow the system program to execute
multiple DOS operation
AC (alignment check) :
 if the word or double word
Is addressed on a non-word or
non-double word boundary
VIF (virtual interrupt flag) :
 copy the interrupt flag bit
(in Pentium 4)

29. VIP (virtual interrupt pending) :
 Give the information about virtual mode
interrupt. Set if interrupt is pending
ID (identification) :
 The ID flag indicate that Pentium 4 micro-
processor support the CPUID or not.
 The CPUID instruction provides the system
with information about microprocessor such
as its version number and manufacturer

30. Segment Register
CS (code segment) :
 area of memory that hold the code
(executable program) used by MP
 Have the starting address of the memory
that hold code
 CS:IP used to access the whole 64k
memory of code segment

31.  SS (stack segment) :
 area of memory used for the stack
 stack is used to store data
 memory 64k can be access by SS:SP
 DS (data segment) :
 area of memory that hold all data
refer by general purpose register
(AX, BX etc. )
64k memory Accessed by using DS and offset
address register

32. ES (extra segment) :
 additional data segment that is used by
some of the string instructions to hold
destination data
 FS and GS :
 supplemental register used as most
extra segment in 64-bit MP. Window use
these segments for internal operation. But
no definition for their usage is available

33. REAL MODE MEMORY ADDRESSING
 The only mode available on the 8086-8088.
20 bit address bus  1 MB, 16 bit data bus, 16 bit registers
 80286 and above operate in either the real or
protected mode.
 Real mode operation allows addressing of only the
first 1M byte of memory space—even in Pentium 4
or Core2 microprocessor.
 the first 1M byte of memory is called the real memory,
conventional memory, or DOS memory system

34. Segment registers hold the base address of where a
particular segment begins in memory. There is the
 code segment (CS)
 data segment (DS)
 stack segment (SS)
 extra segment (ES).

35. Segments and Offsets
 All real mode memory addresses must consist of a
segment address plus an offset address.
 segment address defines the beginning address of any
64K-byte memory segment
 offset address selects any location within the
64K byte memory segment

36. Segments and Offsets
16-bit each
Appended 4 bits (0H)
Segment Start Address
in Segment Register
0
Then the Effective memory Address (EA) =
20-bit segment start address +
16-bit offset address

37. – this shows a memory
segment beginning at
10000H, ending at
location IFFFFH
• 64K bytes in length
– also shows how an offset
address, called a
displacement, of F000H
selects location 1F000H
in the memory
Segments and Offsets

38. Segments and Offsets
 Once the starting address is known, the ending
address is found by adding FFFFH.
 because a real mode segment of memory is 64K in
length
 The offset address is always added to the segment
starting address to locate the data.
[1000:2000H]
 a segment address of 1000H; an offset of 2000H

39. Effective Address Calculations
• EA = segment register (SR) x 10H + offset
(a) SR: 1000H
10000 + 0023 = 10023H
(b) SR: AAF0H
AAF00 + 0134 = AB034H
(c) SR: 1200H
12000 + FFF0 = 21FF0H

41. Default Segment and Offset Registers
 The microprocessor has rules that apply to
segments whenever memory is addressed.
 These define the segment and offset register
combination
[CS:IP]
 The code segment register defines the start of the
code segment.
 The instruction pointer locates the next
instruction within the code segment.

42. Default Segment and Offset Registers
 Another of the default combinations is the stack.
 stack data are referenced through the stack segment at
the memory location addressed by either the stack pointer
(SP) or the base pointer (BP)
 a memory segment can touch or overlap if 64K bytes of
memory are not required for a segment

43. – think of segments as
Windows that can be
moved over any area of
memory to access data or
code
– a program can have more
than four or six segments,
• but only access four or six
segments at a time
Default Segment and Offset Registers
00000
Stack
Code
Data
Extra
0FFFF
10000
1FFFF
20000
2FFFF
30000
33FFF
34000
43FFF
44000
48FFF
49000
58FFF
59000
FFFFF
Memory
1 0 0 0 DS
2 0 0 0 CS
3 4 0 0 SS
4 9 0 0 ES

44. Default Segment and Offset Registers
Code should be limited to
only this portion of the
code segment, to avoid
effects of segment
overlap.

45.  They can occupy completely separate parts of
memory.
 Multiple segments could even coincide because
there are multiple segment registers, the CPU can
keep track of.
 A program can use, multiple segments at the same
time.

47. Default Segment and Offset
Registers
 Default segment numbers in:
 CS for program (code)
 SS for stack
 DS for data
 ES for string (destination) data
 Default offset addresses that go with them
Convention Example: EA = CS:[IP]
Segment Start
in Segment register
Offset: Literal
or in a CPU register

49. TPA
 The Transient Program Area (TPA) holds the DOS
(disk operating system) operating system; other
programs that control the computer system.
 TPA is the first available area of memory above
drivers and other TPA programs
 Area is indicated by a free-pointer maintained by
DOS
 program loading is handled automatically by the
program loader within DOS

50. The TPA also stores any currently active
or inactive DOS application programs.

51. Real Mode Addressing Scheme Allows
Relocation
 A relocatable program is one that can be placed
into any area of memory and executed without
change.
 Segment plus offset addressing allows DOS
programs to be relocated in memory.

52.  This mainly means using relative offsets for data
accesses and jump instructions. If this is easy/possible is
based on the type of architecture, the size of the address
space and the size of the program..
 Relocatable data are data that can be placed in any
area of memory and used without any change to the
program

53. Real Mode Addressing Scheme Allows
Relocation
 Because memory is addressed within a segment
by an offset address, the memory segment can be
moved to any place in the memory system without
changing any of the offset addresses.
.

54.  Only the contents of the segment register must be
changed to address the program
in the new area of memory.
 Windows programs are written assuming that the first 2G
of memory are available for code and data.